Re: [openssl-users] DH parameters [was: Vulnerability logjam downgrades TLS connections to 512 Bit]

2015-05-22 Thread Jeffrey Walton
On Fri, May 22, 2015 at 5:20 AM, Walter H. walte...@mathemainzel.info wrote: Hello On 22.05.2015 08:30, Jeffrey Walton wrote: Or are you talking about server certificates with fixed DH parameters? can you please tell me more about this? They have a DH group called out by parameters (an not

Re: OpenSSL and DH parameters

2013-10-31 Thread Michel
If the negotiated cipher suite for an RSA encrypted client-server session does not involve using the RSA public keys, then when is RSA used in that session ? Not sure to fully understand your question, but the answer may be : 'Just for [server] authentication' Hope this helps.

RE: OpenSSL and DH parameters

2013-10-27 Thread Dave Thompson
From: owner-openssl-users On Behalf Of Viktor Dukhovni Sent: Friday, October 25, 2013 09:46 On Fri, Oct 25, 2013 at 06:35:08AM -0700, LN wrote: I mean in a typical usage of OpenSSL is it mandatory to call SSL_CTX_set_tmp_dh() if I call SSL_CTX_use_certificate() and

RE: OpenSSL and DH parameters

2013-10-27 Thread Dave Thompson
From: owner-openssl-users On Behalf Of Patrick Pelletier Sent: Friday, October 25, 2013 02:53 On 10/24/13 1:59 PM, Dave Thompson wrote: (For EC, the specified curve must also be acceptable to client(s) per ClientHello extension, which encourages using the callback or choosing a popular

Re: OpenSSL and DH parameters

2013-10-25 Thread Patrick Pelletier
On 10/24/13 1:59 PM, Dave Thompson wrote: (For EC, the specified curve must also be acceptable to client(s) per ClientHello extension, which encourages using the callback or choosing a popular curve like P-256.) So, my understanding is that if the tmp_ecdh is set to a curve which is not

Re: OpenSSL and DH parameters

2013-10-25 Thread Viktor Dukhovni
On Thu, Oct 24, 2013 at 11:52:36PM -0700, Patrick Pelletier wrote: (For EC, the specified curve must also be acceptable to client(s) per ClientHello extension, which encourages using the callback or choosing a popular curve like P-256.) So, my understanding is that if the tmp_ecdh is set to

Re: OpenSSL and DH parameters

2013-10-25 Thread LN
Hi, I mean in a typical usage of OpenSSL is it mandatory to call SSL_CTX_set_tmp_dh() if I call SSL_CTX_use_certificate() and  SSL_CTX_use_PrivateKey(). I know that for RSA keys, for example, the session key exchange is done using the public keys of the client and server. If my understanding is

Re: OpenSSL and DH parameters

2013-10-25 Thread Viktor Dukhovni
On Fri, Oct 25, 2013 at 06:35:08AM -0700, LN wrote: I mean in a typical usage of OpenSSL is it mandatory to call SSL_CTX_set_tmp_dh() if I call SSL_CTX_use_certificate() and SSL_CTX_use_PrivateKey(). No, this is optional. I know that for RSA keys, for example, the session key exchange is

Re: OpenSSL and DH parameters

2013-10-25 Thread LN
Is it recommended to specify and use DH parameters for server ? I know that RSA encryption/decryption is slow and this is why RSA public keys are used only for establishing the session key which is a symmetric key usually because symetric key encryption is fast. If the negotiated cipher suite

RE: OpenSSL and DH parameters

2013-10-24 Thread Dave Thompson
Do you mean SSL/TLS the protocols and OpenSSL the implementation? For SSL when an ADH or EDH aka DHE suite is negotiated, the server must send DH parameters and its (nominally one-time) public key, and the client uses or at least matches the parameters and sends its (ditto) public key.

Re: OpenSSL: exchanging DH parameters

2004-01-28 Thread Prakash babu
Hi, I would suggest to have a copy of the same DH params before hand than to exchange during key exchange process because exchanging the key values always exposes you to the man-in-the-middle problem. man-in-the-middle problem. The Diffie-Hellman key exchange is vulnerable to a man-in-the-middle